It is known to form a radial blade wheel with end plates having an outer diameter which is greater than the outer diameter of the blades. This means that the end plates protrude farther than the blades from the rotation axis of the radial blade wheel, whereby an outer space is formed which does not comprise blades. In this solution, the blades are formed in such a way that when the radial blade wheel is rotating, the blades bring, over their whole length, motion energy to the particles flowing along the blades.
An outer space without blades forms a rotating diffuser. The distance between the end plates may increase in the diffuser space in the direction away from the rotation axis. This contributes to decreasing the flow velocity, whereby the outflow velocity from the radial blade wheel is decreased.
A disadvantage with the above radial blade wheel is that the performance of the blade wheel is not optimal.